I find all this new info on spark plugs enlightening, and thought provoking. I used to just ask for "stock big block OE replacements" The parts guy fiddles with their computer and comes back with 8 autolite, delco, or champions depending on the store. Gap em to.045 and snug em in with anti seize. I never really thought into it much, until now. Now Im thinking, "ok lets read the plugs and decide which way to go" How do you know when to go up or down with heat range or plug gap. Black is rich, tan is lean and thick crusty soot is plain bad, but theres gotta be way more to it.